This invention relates to a method of detecting, by utilizing an ultrasonic wave, internal cavities which may be caused in a continuous casting bar of copper or aluminum, for instance, during the continuous casting and rolling process, and an apparatus for practicing the method.
The internal cavities in a casting bar may cause thermal cracks to occur in the succeeding rolling process, and may result in the breaking of the bar during the cold process (drawing and rolling) following the rolling process.
Accordingly, it is necessary to detect the internal cavities in the casting bar on line in the continuous casting and rolling process thereby to control the continuous casting conditions and the quality of the casting bar itself.
Heretofore, a continuous on-line ultrasonic flaw detection method has not been employed in a continuous casting and rolling process.
In a conventional ultrasonic flaw detection method employing a water jet system or a water membrane gap system, the temperature of a material to be inspected is relatively high, and therefore a water evaporating area appears near the surface of the material to be inspected, which interrupts the transmission of the ultrasonic wave, as a result of which the detection cannot be carried out. This is a drawback accompanying the conventional ultrasonic flaw detection method.